Solid-phase micro extraction (SPME) is based on the partition/adsorption of analytes to a stationary phase coated on a fused-silica fiber. SPME is an attractive alternative to traditional sample treatment and preparation methods, because it combines sample extraction, pre-concentration following by sample introduction, altogether into one step and can be readily combined with gas chromatography (GC) or high performance liquid chromatography (HPLC). This method has gained increasing application in many areas including environmental, food and drug analysis.
Almost all commercially available SPME fibers are based on fused-silica fiber. The coating techniques include pasting with adhesives, electrochemical polymerization or deposition, direct-pasting, chemical corrosion, and the sol-gel technique.
In general, organic polymers are the most widely used coatings for the extraction of organic compounds. However, some inorganic coatings based on graphite materials and metallic compounds have also exhibited good performance in SPME.
Adsorption of compounds depends on the functional groups on the stationary phase and surface area. Increasing the surface area increases the sensitivity of analysis and lowers the limit of detection. In this way, metal oxides such as Al2O3, ZnO, ZrO2, and nanostructure PbO2 prepared by electro-oxidizing or electro-deposition techniques have been used as SPME coatings. Metal oxide-based SPME coatings made of a mixture of Al2O3 on a polyvinylchloride matrix dispersed in tetrahydrofuran and Nb2O5 coating using a metallo-organic decomposition technique have also been successfully used.
By applying an inexpensive and effective aqueous growth technique at mild temperatures functionalized coating of metal oxide materials on fused silica is achieved. Such a technique allows the generation of advanced nano/micro particulate coatings without using any template, membrane, surfactant, applied external fields, or specific requirements in fused silica activation, thermal stability, or crystallinity. Such a process avoids the safety hazards of organic solvents and their eventual evaporation and potential toxicity. In addition, because no organic solvents or surfactants are present, the purity of the materials is substantially improved. The residual salts are easily washed out by water due to their high solubility. In most cases, no additional heat or chemical treatments are necessary, which represents a significant improvement compared with surfactant, template, membrane base, corrosion or electrochemical synthesis methods.
The present invention method is applicable to all water-soluble metal ions likely to precipitate in solution.
Therefore, it would be advantageous to provide a method to overcome the above shortcomings.